The present invention relates to an electric generator system which is operated by the energy of exhaust gases emitted from an internal combustion engine.
Various systems have heretofore been proposed for recovering the energy of exhaust gases discharged from an internal combustion engine, in the form of electric energy into which the exhaust energy is converted. One such system is disclosed in Japanese Laid-Open Patent Publication No. 63-95124, for example.
The above publication discloses an exhaust-driven electric generator which is mounted on the shaft of a turbine drivable by the energy of exhaust gases and which is operable by the exhaust energy to generate electric power. Since the generator is mounted on the turbine shaft without the intermediary of any power transmitting device to drive the generator, the generator can be driven with good efficiency. However, because only one turbine is driven by the exhaust energy, the efficiency of the turbine varies depending on changes in the temperature and amount of the exhaust gases discharged by the internal combustion engine, and hence the efficiency with which the exhaust gas is recovered is not of a satisfactorily high level. More specifically, an internal combustion engine mounted on an automobile has a wide range of operational parameters, i.e., the temperature and amount of exhaust gases emitted from the engine vary in a wide range. If a turbine that matches a high temperature and a large amount of exhaust gases discharged when the engine operates under a high load and at a high speed is selected for use with the engine, then the efficiency of the turbine is greatly lowered when the temperature and amount of exhaust gases are low at the time the engine operates under a low load and at a low speed. On the contrary, if a turbine matching a low temperature and a small amount of exhaust gases emitted when the engine operates under a small load and at a low speed is selected for use with the engine, then the efficiency with which the exhaust gas is recovered is also lowered when the temperature and amount of exhaust gases ar increased in high-load and high-speed operation of the engine, since the exhaust gases have to be partly discharged in bypassing relation to the turbine in order to avoid destruction of the turbine.